What is Behind the Spread of Lyme Disease?

I have written several articles the environment. A list of links have been provided at bottom of this article for your convenience. This article will, however address different aspects on the environment and the planet in general.

Lyme disease is the most common vector-borne disease in the United States. Lyme disease is caused by the bacterium Borrelia burgdorferi and rarely, Borrelia mayonii. It is transmitted to humans through the bite of infected blacklegged ticks. Typical symptoms include fever, headache, fatigue, and a characteristic skin rash called erythema migrans. If left untreated, infection can spread to joints, the heart, and the nervous system. Lyme disease is diagnosed based on symptoms, physical findings (e.g., rash), and the possibility of exposure to infected ticks.  Laboratory testing is helpful if used correctly and performed with validated methods. Most cases of Lyme disease can be treated successfully with a few weeks of antibiotics. Steps to prevent Lyme disease include using insect repellent, removing ticks promptly, applying pesticides, and reducing tick habitat. The ticks that transmit Lyme disease can occasionally transmit other tickborne diseases as well.

Lyme disease is an illness caused by borrelia bacteria. Humans usually get Lyme disease from the bite of a tick carrying the bacteria.

Ticks that can carry borrelia bacteria live throughout most of the United States. But Lyme disease is most common in the upper Midwest and the northeastern and mid-Atlantic states. It’s also common in Europe and in south central and southeastern Canada.

You’re at risk of Lyme disease if you spend time where the ticks live, such as grassy, brushy or wooded areas. Taking safety measures in these areas can lower the risk of Lyme disease.


A tick bite may look like as a tiny, itchy bump on your skin, much like a mosquito bite. This doesn’t mean you have a tick-borne disease. Many people will not notice they’ve had a tick bite.

The symptoms of Lyme disease vary. They usually show up in stages. But the stages can overlap. And some people don’t have symptoms of the typical early stage.

Stage 1

Lyme disease rash on different skin colors.Lyme disease rashEnlarge image

Early symptoms of Lyme disease usually happen within 3 to 30 days after a tick bite. This stage of disease has a limited set of symptoms. This is called early localized disease.

A rash is a common sign of Lyme disease. But it doesn’t always happen. The rash is usually a single circle that slowly spreads from the site of the tick bite. It may become clear in the center and look like a target or bull’s-eye. The rash often feels warm to the touch, But it’s usually not painful or itchy.

Other stage 1 symptoms include:

  • Fever.
  • Headache.
  • Extreme tiredness.
  • Joint stiffness.
  • Muscle aches and pains.
  • Swollen lymph nodes.

Stage 2

Without treatment, Lyme disease can get worse.  The symptoms often show up within 3 to 10 weeks after a tick bite. Stage 2 is often more serious and widespread. It is called early disseminated disease.

Stage 2 may include the stage 1 symptoms and the following:

  • Many rashes on other parts of the body.
  • Neck pain or stiffness.
  • Muscle weakness on one or both sides of the face.
  • Immune-system activity in heart tissue that causes irregular heartbeats.
  • Pain that starts from the back and hips and spreads to the legs.
  • Pain, numbness or weakness in the hands or feet.
  • Painful swelling in tissues of the eye or eyelid.
  • Immune-system activity in eye nerves that causes pain or vision loss.

Stage 3

In the third stage, you may have symptoms from the earlier stages and other symptoms. This stage is called late disseminated disease.

In the United States, the most common condition of this stage is arthritis in large joints, particularly the knees. Pain, swelling or stiffness may last for a long time. Or the symptoms may come and go. Stage 3 symptoms usually begin 2 to 12 months after a tick bite.

The type of Lyme disease common in Europe can cause a skin condition called acrodermatitis chronic atrophicans. The skin on the backs of the hands and tops of the feet get discolored and swell. It also may show up over the elbows and knees. More-serious cases may cause damage to tissues or joints.

This skin condition may show up many months to many years after a tick bite.

When to see a doctor

Most people who get Lyme disease don’t remember having a tick bite. And many symptoms of Lyme disease relate to other conditions. See your health care provider if you have Lyme disease symptoms. An early diagnosis and proper treatment can improve outcomes.

If you know you had a tick bite or might have been around ticks, watch for symptoms. If they show up, see your care provider as soon as possible.

Lyme Disease (Tick-borne borreliosis, Lyme arthritis) Fact Sheet

Last Reviewed: July 2017

What is Lyme disease?

Lyme disease is an infection caused by the bacteria Borrelia burgdorferi and is spread to humans through the bite of infected blacklegged ticks (or deer ticks). Not all deer ticks are infected with the bacteria. Lyme disease can affect people of any age. A vaccine for Lyme disease is not currently available. Lyme disease is the most prevalent tick-borne disease in New York and has been reportable since 1986.

Who gets Lyme disease?

Lyme disease can affect people of any age. People who spend time outdoors in activities such as camping, hiking, golfing, or working or playing in grassy and wooded environments are at increased risk of exposure. The chances of being bitten by a deer tick are greater during times of the year when ticks are most active. Ticks can be active any time the temperature is above 45° F. Young deer ticks, called nymphs, are active from mid-May to mid-August and are about the size of poppy seeds. Adult ticks are most active from March to mid-May and from mid-August to November and are about the size of sesame seeds. Both nymphs and adults can spread Lyme disease. Infected deer ticks can be found throughout New York State.

How is Lyme disease spread?

Not all deer ticks are infected with the bacteria that cause Lyme disease. Ticks can become infected if they feed on animals such as mice and other mammals that are infected. The disease can be spread when an infected tick bites a person and stays attached for a period of time. In general, the tick must be attached for 36 to 48 hours or more. Lyme disease does not spread from one person to another. Transfer of the bacteria from an infected pregnant woman to her fetus is extremely rare.

What are the signs and symptoms of Lyme disease?

Early symptoms usually appear within 3 to 30 days after the bite of an infected tick. In 60-80 percent of cases, a circular bull’s eye rash about two inches in diameter, called erythema migrans, appears and expands around or near the site of the tick bite. Sometimes, multiple rash sites appear. One or more of the following symptoms usually mark the early stage of Lyme disease: chills and fever, headache, fatigue, stiff neck, muscle and/or joint pain, and swollen glands. If Lyme disease is unrecognized or untreated in the early stage, more severe symptoms may occur. As the disease progresses, severe fatigue, a stiff aching neck, and tingling or numbness in the arms and legs, or facial paralysis can occur. The most severe symptoms of Lyme disease may not appear until weeks, months or years after the tick bite. These can include severe headaches, painful arthritis, swelling of the joints, and heart and central nervous system problems.

How is Lyme disease diagnosed?

Symptoms and possible tick bite exposure may cause a health care provider to suspect Lyme disease. If suspected, lab tests can be performed to confirm diagnosis.

What is the treatment for Lyme disease?

Patients treated with antibiotics in the early stages of Lyme disease usually recover quickly and completely. Antibiotics commonly used for treatment include doxycycline, amoxicillin, or cefuroxime axetil. Patients with certain neurologic or cardiac forms of illness may require additional treatment. It is important to speak with your health care provider if you think you might have Lyme disease. The best treatment for Lyme disease is prevention and awareness.

Does past infection with Lyme disease make a person immune?

Lyme disease is a bacterial infection. Even if successfully treated, a person may become re-infected if bitten later by another infected tick.

What can be done to prevent Lyme disease?

The best prevention of Lyme disease is through awareness. Generally, ticks cannot jump or fly onto a person. They wait in vegetation and cling to animals and humans when they brush by. When in a potentially tick-infested habitat (wooded and grassy areas) take special care to prevent tick bites, such as wearing light-colored clothing (for easy tick discovery) and tucking pants into socks and shirt into pants. Check after every 2 to 3 hours of outdoor activity for ticks on clothing or skin. Brush off any ticks on clothing or skin before skin attachment occurs. A thorough check of body surfaces for attached ticks should be done at the end of the day. If removal of attached ticks occurs within 36 hours, the risk of tick-borne infection is minimal. For proper tick removal, please watch the video at Tick removal. A vaccine for Lyme disease is not currently available.

Insect repellents can be effective at reducing bites from ticks that can spread disease. If you decide to use a repellent, use only what and how much you need for your situation. More information on repellents can be found at Environmental Protection Agency – insect-repellents.

In addition:

  • Be sure to follow label directions.
  • Try to reduce the use of repellents by dressing in long sleeves and pants tucked into socks or boots.
  • Children should only handle repellents with adult supervision. Adults should apply repellents to their own hands first and then gently spread on the child’s exposed skin. Avoid applying directly to children’s hands. After returning indoors, wash your child’s treated skin and clothing with soap and water or give the child a bath.
  • Do not apply near eyes, nose or mouth and use sparingly around ears.
  • After returning indoors, wash treated skin with soap and water.

Domestic animals can carry ticks into areas where you live so it is important to check pets for ticks before they enter the home.

How should a tick be removed?

Grasp the mouthparts with tweezers as close as possible to the attachment (skin) site. Be careful not to squeeze, crush or puncture the body of the tick, which may contain infectious fluids. Pull firmly and steadily upward to remove the tick. After removing the tick, thoroughly disinfect the bite site and wash hands. The NYSDOH has created a video on proper tick removal (Proper Tick removal) and a printable card with steps on how to remove ticks (How to Remove a Tick Card). See or call a doctor if there are concerns about incomplete tick removal. Do not attempt to remove ticks by using petroleum jelly, lit cigarettes or other home remedies because these may actually increase the chance of contracting a tick-borne disease.

Lyme disease is spreading fast—but a vaccine may be on the way

Several vaccines and new treatments are in the works as the ticks that carry the disease spread to new locations. Here’s what you need to know about tick bites and your risk of infection.

It’s Lyme season in the United States and the risk of infection by the black-legged ticks that carry it is growing, especially with half of Americans now living on tick infested territory.

Without immediate antibiotic treatment, Lyme disease can cause debilitating heart and nervous system issues, arthritis, and other complications, making it difficult to cure. Although several vaccines are in development, the rising number of cases have reached epidemic levels: in the U.S., some 476,000 cases are reported each year accounting for about $1 billion in medical costs.

It’s become “a true health threat,” says Paul Mead, chief of the bacterial diseases branch at the United States Centers for Disease Control and Prevention. “Clearly there is a need for new interventions and preventions.”

A microscopic view of the spiral-shaped bacteria, Borrelia burgddorferi, which causes Lyme disease. The bacteria appears as bright orange or green, depending on which surface protein the fluorescent antibodies bind to the surface.
An Axial MRI that visualizes enlargement of the central ventricles in the brain of a patient suffering from chronic lyme disease.

Left: The Lyme disease bacterium, Borrelia burgdorferi, is a parasite that cycles between ticks and vertebrate hosts. B. burgdorferi alters the proteins expressed on its outer surface, depending on the state of each host. In this light micrograph, immunofluorescent a…Read More

Right: A contrast axial magnetic resonance imaging (MRI) scan of the brain of a 41-year-old man with Lyme encephalopathy. The scan shows abnormal areas around the ventricles, a sign of the chronic brain and spinal cord inflammation that occurs in this condition.

With several vaccines in development, researchers are optimistic they will be able to prevent the disease within just a few years. A human vaccine developed by Pfizer and its French biotech partner, Valneva, is in Phase 3 trials. Moderna is working on an mRNA version. Researchers at MassBiologics of UMass Chan Medical School are developing an anti-Lyme antibody treatment.

Diagnosing a bite

It’s easy to overlook a tick bite.

After cleaning out a shed at his home in Maryland in March 2005, radio personality at Sirius XM Radio, Earle Baily, discovered what he assumed was a spider bite. Some weeks later, he struggled with pains shooting down his extremities. Over the next months, neurological symptoms developed: he lurched to the right when walking, his joints ached, and his skin was so sensitive that touch felt like the slice of a blade. His hand movements were jerky, and one day, he couldn’t unlock his front door.

He went through six doctors and a litany of misdiagnoses.

Bailey eventually realized he must have been bitten by a blacklegged tick and had Lyme disease. Finally, an internal medicine specialist in North Bethesda, B. Robert Mozayeni, confirmed his suspicions that fall, assuring him, “I’m going to make you better.” He prescribed a cocktail of heavy antibiotics, tinctures, and vitamins. It was a two-year ordeal, but Bailey recovered and is still broadcasting, on the air.

It’s not surprising that the medical profession failed to recognize his condition when he was bitten 18 years ago, since Lyme disease was a relatively new condition and was appearing in new locations. But missed diagnoses continue to be a common problem today. 

The discovery and spread of a tick-borne scourge

It’s been nearly half a century since the disease was first recognized in Old Lyme, Connecticut in 1975. It drew attention when a cluster of children developed unexplained, rheumatoid arthritis-like symptoms. In 1982, medical entomologist and self-described “tick surgeon” Wilhelm Burgdorfer identified the culprit: a previously undiscovered spiral bacteria, Borrelia burgdorferi. The pathogen passes to humans through the bite of a black-legged (or deer) tick, but not all of them are carriers. A second, less prevalent Lyme bacterium, B. mayonii, was later found in the U.S.; two other speciesB. afzelii and B. garinii—are responsible for most European infections. In western Europe, 200,000-plus cases are diagnosed each year.

Ticks pick up the bacteria while feeding on infected hosts, including white-footed mice (the primary disease reservoir), other small mammals, and white-tailed deer. B. burgdorferi then sits in a tick’s intestine for months until the arthropod latches onto a new victim for its next meal. With the influx of blood into the tick’s gut, the bacteria transform. They stop producing an outer surface protein, OspA, that anchors them to the intestine, which allows them to move to the tick’s salivary glands. The bacteria then pass through the wound and into their new host.

The process from bite to transmission typically takes 36 to 48 hours—so finding and removing a tick quickly after being bitten is critical.

What happens next isn’t always predictable. A signature bull’s eye rash may signal infection, but not always. The bacteria may initially remain localized, or rapidly disseminate throughout the body.

Preventing infection

During Bailey’s first appointment with Mozayeni, the doctor lamented that if he were a dog, he could have been vaccinated against Lyme disease: Canine vaccines have been around for decades.

There was a human vaccine, LYMErix, approved by the FDA in 1998, but it was discontinued after three years. Anti-vaccine campaigns and lawsuits claiming reactions killed sales, though inquiry by the FDA found no indication that the vaccine caused harm.

With this stigma, drug makers avoided research into new human Lyme vaccines until recently. But the challenge now is creating vaccines that will protect against the seven globally known strains of Lyme disease, says Obadiah Plante, who leads the bacteriology team at Moderna.

Both of the human vaccine candidates currently in development target the bacterium’s OspA protein, creating antibodies that prevent the organisms from suppressing OspA when the tick next feeds. This will render them immobile, imprisoned within the tick’s intestine and unable to infect a human host.

The Pfizer/Valneva candidate, VLA15, is farthest along and is being tested in a phase three clinical trial that launched in the summer of 2022. The goal is to enroll about 6,000 people aged five and older in 50 Lyme-endemic communities in the U.S., Finland, Germany, the Netherlands, Poland, and Sweden. The companies are testing safety and efficacy of a three-dose vaccine, followed by a booster, designed to protect against Lyme bacteria strains prevalent in both North America and Europe.

However, trials at study sites in Nantucket and Martha’s Vineyard were abruptly halted in February, disqualifying about half of the study’s participants. In a statement, Pfizer cited violation of international Good Clinical Practice protocols by a third-party operator, Boston-based Care Access. They told the press that there were no safety concerns or vaccine reactions prompting their decision.

In an email, a spokesperson for Pfizer noted that the study is expected to wrap up in December 2025, but the company declined an interview until it has new results to report.

Moderna is currently applying mRNA technology—proven successful with its COVID vaccine—to bacterial vaccines, with an initial focus on Lyme disease. The company will launch human trials this summer with 800 participants in the U.S. between 18 and 70 years old. They will test two vaccines: The first, named mRNA-1982 to honor Wilhelm Burgdorfer’s work, contains a single mRNA that targets the Borrelia bacteria species that causes most cases of Lyme disease in the U.S.

The second, named mRNA-1975 to commemorate the year Lyme disease was identified, contains a mixture of seven mRNAs targeting the Borrelia species that cause most cases of Lyme disease in both the U.S. and Europe.

MassBiologics is using a different approach. Instead of stimulating the body to produce antibodies, as vaccines do, this method introduces a single monoclonal antibody targeting OspA. The benefit: “Within days after you get the subcutaneous injection, you’ve absorbed enough of the antibody so you’re immediately immune,” says Mark Klempner, a professor of medicine and vice chancellor emeritus of MassBiologics at UMass Chan Medical School. In contrast, vaccines currently in development may take six months to confer immunity.

In lab studies, when about 20 infected ticks were placed on nonhuman primates, this antibody treatment provided 100 percent protection. Klempner says that they may produce two or three products lending protection varying from perhaps two to seven months or more. He is hopeful that they’ll be ready to apply for approval from the FDA in 2025.

Lyme season 

Lyme disease risk is seasonal, and the U.S. is entering prime tick time. “Over 80 percent of infections occur between May and September,” says Klempner. But ticks may begin “questing”—seeking a blood meal—when the mercury hits 45° F. Extra vigilance is needed when last years’ larvae emerge as tiny nymphs in June and July: they’re the size of a poppyseed and may already be infected.

Meanwhile, the distribution and incidence of Lyme disease continues to expand and increase, says Sam Telford, a tick expert and professor of infectious disease and global health at Tufts University.

The Northeast, mid-Atlantic and upper Midwest are epicenters for Lyme infection, with the large majority of cases reported from Maine to Virginia and in Wisconsin, Minnesota, and Michigan. But the black legged ticks that carry the disease are moving north, south, and west.

As climate change brings warmer winters, these eight-legged parasites settle into previously uninhabitable territory. But human alteration of the landscape—suburban development—is the main driver, says Telford. Fragmented forest creates ideal habitat for the mice, other rodents and deer that harbor Lyme-causing bacteria. Today, more than 50 percent of the U.S. population shares territory with black legged ticks. Lyme disease is the most common vector-borne disease in the Northern Hemisphere.

Cases have remained stable for a decade, but the numbers are misleading: Heavily affected states like Massachusetts and New York have reduced surveillance efforts because of the tremendous resources needed to count so many infections, CDC’s Mead says. The epidemic caseload underscores the need for a variety of effective tools. “We need something to help drive down this disease,” Mead adds.

There are things people can do now to protect themselves until new preventions are available: using repellents, showering after time outdoors, and cleaning up yard leaf litter. It’s also important to know the signs of tick-borne illness—an unexplained fever or a rash—and seek medical care, Mead says. “The great majority of Lyme disease cases can be treated pretty effectively with antibiotics, if you recognize it early.”

Lyme Disease is On the Rise – An Expert Explains Why

May marks the beginning of the summer season when black-legged ticks that spread Lyme disease are more prevalent – even in California.

Earlier this month, the U.S. Centers for Disease Control and Prevention (CDC) reported that cases of tickborne diseases had more than doubled from 2004 to 2016, from 22,000 to 48,000, and that Lyme disease accounted for 82 percent of tickborne diseases.

Charles Chiu
Charles Chiu, MD, PhD

Moreover, due to underreporting, the actual number of Lyme disease cases is estimated to be significantly higher – likely more than 350,000 in 2016. 

We talked to infectious disease expert Charles Chiu, MD, PhD, about the rise in Lyme disease cases, better diagnostic tests on the horizon and what you need to know to protect yourself from infection. Chiu is an associate professor of laboratory medicine and medicine and director of the UCSF-Abbott Viral Diagnostics and Discovery Center.

How common is Lyme disease in California? And why have rates been increasing?

In terms of reported cases, there are about 80 to 100 a year in the state. Residents in or travelers to the northwestern coastal counties – Trinity, Humboldt, and Mendocino – are at highest risk. But because of underreporting, the actual number of Lyme disease cases likely exceeds 1,000 cases a year, simply because most cases of Lyme disease are not reported.

There are several potential reasons why rates have increased in California and nationwide. One is globalization. People travel extensively, and for instance, someone could get infected while on the East Coast and come back with Lyme disease.

Another reason is climate change, in that the geographic range of the tick vector, which is the Ixodes or black-legged tick, has expanded westward from the northeast United States as well as southward year after year. For ticks to be maintained in nature, they need to have what we call an animal reservoir, essentially a mammal such as a squirrel or rodent that can harbor Borrelia burgdorferi – the bacterium in the tick that causes Lyme disease. Therefore, expansion of the animal reservoir is also another reason for increasing Lyme disease rates. On the East Coast, the reservoir is the white-footed mouse. In California, the Western gray squirrel harbors the bacterium. Lizards, while not a reservoir for Borrelia burgdorferi, are common hosts for the black-legged tick in California so increase the risk of infections to humans by maintaining the tick population in the wild.

How is Lyme disease transmitted, and is it contagious between humans?

Borrelia burgdorferi causes asymptomatic infection in these small mammal reservoirs. When the ticks feed on mammals carrying Borrelia burgdorferi, these ticks get infected. They can then transmit the infection to humans. 

However, humans are considered a dead-end host because the efficiency of transmitting the bacterium to other humans is extremely low. The period during which you can find the bacterium in blood is very brief, generally a few days at most, and blood-borne transmission of Borrelia burgdorferi, such as by transfusion, has never been reported. Borrelia burgdorferi is also not excreted in other body fluids such as sweat, urine, saliva, or respiratory secretions. Lyme disease is therefore not considered contagious.

Compared to other infections, is Lyme disease more difficult to detect and diagnose?

microscopic image of Borrelia burgdorferi
Borrelia burgdorferi, the bacterium that causes Lyme disease. Image by NIH

It does appear that Lyme disease is harder to diagnose, and it’s because the Borrelia burgdorferi very rapidly leaves the blood and disseminates into the lymph nodes and into tissues. As a result, blood tests for early Lyme disease have low sensitivity.

Why is it important to accurately diagnose Lyme disease?

Timely and accurate diagnosis of Lyme disease can help prevent potential complications, which include encephalitis, a brain infection; myocarditis, a heart infection; or endocarditis, a heart valve infection.

Is it true that it takes at least 24 hours for a tick to transmit Lyme disease to you?

Yes, this is true. The CDC recommends that patients who notice the tick and remove it within 24 hours do not need antibiotic prophylaxis with doxycycline to prevent Lyme disease transmission. The tick typically needs to be on you, basically sucking your blood and attached to you for 36 to 48 hours, during which the Borrelia burgdorferi migrates from the tick gut to its salivary glands, before it can transmit the Lyme pathogen.

So it’s definitely important to find the ticks early and get them off you.

Yes, I recommend that after you go hiking or camping or are otherwise potentially exposed to ticks, that you always do a tick check. The ticks that are most likely to transmit the bacterium are young nymphal ticks. They’re about the size of a poppy seed, so they’re extremely small.


  • The western black-legged tick has been found in 56 of the 58 counties in California.
  • It is common in the humid north coastal areas and on the western slope of the Sierra Nevada range.
  • Ticks prefer cool, moist areas and can be found on wild grasses and low vegetation in both urban and rural areas.
  • Adult ticks climb to the tip of vegetation along trails and wait for a host to brush against them.
  • Nymphs are found in low, moist vegetation such as leaf litter and on logs.
  • Adults are most active from fall through early spring and the nymphs are active primarily in the spring and early summer months.

Source: California Department of Public Health

Ticks do not jump or fly. What they do is called “questing,” which means that they wait at the ends of grass or foliage and when you brush by, they’ll immediately latch onto your leg or onto your clothing. But you really need to conduct a tick check all over your body because you won’t necessarily get bitten by the tick where the grass contracted your leg. Ticks can crawl to your armpit or groin and bite there, for instance.

What percentage of black-legged ticks carry Lyme?

It can be fairly high, anywhere from 2 percent to 15 percent among nymphal ticks in California, depending on the geographic location and season.

How accurate are the current diagnostic tests for Lyme disease? And why do many cases remain undiagnosed?

The current approved testing for Lyme disease is a two-tier serologic test that looks for the generation of antibodies in response to the infection.

But the key limitation of the serologic test in early Lyme disease is that typically an infected individual may take several weeks before he or she is able to mount an antibody response. Therefore, in early Lyme disease, the test sensitivity is only about 30 to 40 percent.

Now after a person generates antibodies after three to four weeks, then the two-tiered serologic test tends to be very sensitive and is good for determining whether a patient was infected.

The take-home message is that we do not have an accurate test for early Lyme disease, and this is why the diagnosis is generally made clinically by a physician and also why there is so much underreporting.

If a patient presents with fever, a bull’s-eye rash, and during tick season with tick exposure, this, according to CDC criteria, is enough to make a diagnosis of Lyme disease. Part of the reason why laboratory testing isn’t an essential criterion for the diagnosis of Lyme disease is that we simply don’t have a test that is conclusive.

Your lab is working on better diagnostics for Lyme disease. How is your new test different?

The big area of clinical need is the ability to diagnose early Lyme disease before you can reliably detect it by antibody testing. Usually that window is zero to one month following the tick bite.

About two years ago, we did RNA sequencing of blood samples from patients with Lyme disease to look at the human host response. We looked at the pattern of gene expression in patients following infection, comparing the gene signature of Lyme disease to that for control patients. And we found that Lyme disease, interestingly enough, has a very distinct pattern of human gene expression in response to the infection.

We used this data in a follow-up study – which is currently unpublished – to develop a test with more than 90 percent accuracy in diagnosing early Lyme disease in patients presenting have a fever and rash, generally seven to 10 days after the tick bite.

It’s really a completely new category of diagnostic tests made possible because of advances in sequencing over the past several years.

What is currently the best standard of care for treatment of Lyme disease?

The standard of care for early uncomplicated Lyme disease recommended by the CDC is 10 to 21 days of doxycycline, which is an oral antibiotic that you take twice a day. Patients admitted to the hospital with severe complications of disseminated Lyme disease, such as meningitis or endocarditis, typically receive a two- to four-week course of an intravenous antibiotic such as ceftriaxone.

If you get Lyme disease once, can you get it again?

Yes, you can, because protective antibody immunity can wane after several years and you may also be infected by a different strain of Borrelia burgdorferi.

There’s a Lyme disease vaccine for dogs, why isn’t there one for humans?

There actually was a vaccine called LYMErix that was approved by the FDA in 1998. But four years later, it was withdrawn from the market. At the time, there were questions involving the safety of the vaccine, concerns raised by anti-vaccine groups, cost, burdensome vaccination schedule (three doses a year), uncertainty regarding efficacy and need for boosters, and low public demand.

I think that there are now some efforts underway to bring back either this vaccine or other vaccines onto the market, especially given the rise of Lyme disease. This is a disease that infects more than 300,000 people a year, so it’s certainly something for which a vaccine would be really helpful.

Why do some patients with Lyme disease show persistent symptoms, even after being treated for the disease with antibiotics?

A small percentage of patients with Lyme disease – depending on the study, 5 to 15 percent – exhibit persistent symptoms after treatment, which can include chronic fatigue, muscle and joint pain, headaches, episodes of “dizziness” or blackouts, cognitive difficulties and/or arthritis. After six months, given significant impairment in quality of life, these patients may be diagnosed with PTLDS (post-treatment Lyme disease syndrome).

We don’t know the cause of PTLDS, or why some patients develop this. Some hypotheses are that the Borrelia burgdorferi bacterium causes persistent infection somewhere in the body or that the symptoms are due to an aberrant immune response to Lyme infection, such as autoimmune disease.

What do you see as the next step in Lyme disease research?

Part of the reason why we haven’t been seeing, clinical trials, vaccines, or drugs for Lyme disease is that we don’t have an accurate diagnostic test, and we would have no way of monitoring, for instance, effectiveness of a prospective vaccine or drug therapy in a clinical trial. We really need the diagnostic test to guide our potential treatments or prevention methods for the bacterium. I think it’s really going to be the development of better diagnostics that will drive potential therapies forward.

A second critical next step is identifying why is it that a proportion of patients with Lyme disease exhibit persistent symptoms that can last for months to years. We need to identify both the cause of PTLDS and identify potential treatments.

What’s really behind the spread of Lyme disease? Clue: it’s not the Pentagon

After my tick bite I realised that the climate crisis was a more likely culprit than any conspiracy theory about weaponisation.

The first indication I’d picked up a tick-borne disease three years ago was the excruciating arthritic pain in my feet as I hobbled to a dinner party at a neighbour’s house in Jerusalem.

Later that night I experienced flu-like symptoms, including a raging fever that, even with antibiotics, would last for more than a week.

It was my wife who noticed the rash spreading across my back, which, with the black halo around the bite on my ankle, was the give-away. It was a form of spotted fever caught from an infected dog tick in the Palestinian territories.

The infectious agent is a bacteria called Rickettsia – identical in transmission and very similar in symptoms to Lyme disease and Rocky Mountain fever. I had caught the Mediterranean cousin, which is known variously as tick typhus or Boutonneuse fever and whose defining feature, in addition to the symptoms shared with Lyme disease, is a vicious rash.

This week tick-borne diseases – specifically Lyme disease – were catapulted into the headlines because of claims in a book, championed by a US congressman, that the current incidence in the US, where tens of thousands of cases of Lyme disease a year are being identified, may have been caused by a shadowy US bioweapons programme that deliberately infected ticks.

The story, picked up around the world and shared virally on social media, has given credence to the book and its author, Kris Newby, who had been struggling to gain recognition for her theory amid a smattering of largely sceptical reviews.

Those reviews noted the thinness of the evidence of her central claim.

Others have noted the improbability of creating a bioweapon out of a slow-moving tick confined to specific habitats and using a disease that takes time to develop and is easily treated with antibiotics.

Vice News called it a “conspiracy theory”. Phil Baker, executive director of the American Lyme Disease Foundation, told the news site: “There’s evidence in the US that Lyme disease was here before Columbus came around. Plus, Lyme disease isn’t life-threatening, so it’s not a good candidate for a biological weapon.”

Lyme disease affects 400,000 Americans each year.

A colleague of Willy Burgdorfer, who first identified the organism responsible for Lyme disease and is accused of weaponising it, was equally damning in the Washington Post. Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, told the paper: “This is again another one of those unfortunate situations where the science fiction of these issues overwhelms the truth.”

The reality, as experts make clear, is that variants of tick-borne infections such as Lyme disease are a global problem. The World Health Organization makes clear that they spread from forested areas of Asia, north-western, central and eastern Europe, as well as the US.

The highly contentious debate – both among scientists and a wider public – over the nature of Lyme disease and its treatment is, however, specific to the US. At times it has lurched into wild and cranky speculation.

If Lyme disease is spreading, it is almost certainly nothing to do with mysterious US bioweapons programmes but instead more mundane human impacts on, and interaction with, the environment.

In the US that includes the continuing sprawl of suburbs and exurbs into places where infected ticks, and disease hosts such as chipmunks and deer, are still common. This is the explanation of the US Centers for Disease Prevention and Control.

Another explanation for the believed spread of the disease since the 1930s – even before Burgdorfer had identified and named it – is the large increase in the population of deer, one of the key hosts of the disease, in the northeastern US after the Depression.

All of which, as argued recently by Katharine Walter who has been studying ticks at Yale University, may have been exacerbated by the climate crisis. Her genome research suggests that Lyme disease has been present in the US for more than 60,000 years.

“Warmer winters and longer summers let more ticks survive and thrive further north each year,” she says. “Tick eggs hatch sooner and ticks spend more time questing for blood, and so are increasingly likely to feast on a human and pass on a disease-causing pathogen. Because more ticks survive and mature more quickly, diseases can be transmitted faster.”

None of which, needless to say, is garnering social media shares in the tens of thousands.

As I write this, I am heading to the vast forests and lakes of Minnesota’s Boundary Waters region where Lyme-infected deer ticks are commonplace.

I’ll be doing what I should have done on the West Bank when I got bitten three years ago. I’ll be tucking long trousers into socks, spraying my trouser legs with tick repellent, zipping up my tent, and checking clothes and what little hair I have left for any ticks.

Because, in the final analysis, it is humans venturing where ticks live that is the most likely cause of the spread of these diseases, combined with global heating. And that last point is sinister enough without adding bioweapons to the mix.

Lyme disease is on the rise. Why is there still no vaccine?

Two decades after a vaccine was withdrawn, scientists are producing new medicines to fend off a disease that experts estimate afflicts nearly half a million people each year.

Imagine trying to medicate a bug.

That was the task taken on by a group of researchers at MassBiologics of UMass Chan Medical School (UMass Chan) in Massachusetts: They developed a way to get an antibody into ticks to neutralize the bacterium that causes Lyme disease, the most common vector-born disease in the United States.

But no, the researchers did not give shots to ticks. They injected the antibody into humans so that people can transmit the antibody to ticks that bite them.

“We are trying to deliver a medicine to a tick so that it doesn’t pass on the infection to the patient,” says Mark S. Klempner, MD, a professor of medicine at UMass Chan. “The patient provides the vehicle to deliver the antibody to the infected tick.”

Targeting ticks to prevent Lyme rather than fighting off an infection after it begins is the fundamental strategy behind three projects that aim to create the only medication to prevent the disease in people. The disease sets off a series of escalating symptoms, starting with a red rash, fatigue, fever, headache, and a mild stiff neck, and sometimes escalating if left untreated to serious complications to joints (arthritis), the heart, and the nervous system.

The current projects come two decades after the first human Lyme vaccine, LYMErix, was pulled from the market because of factors that researchers believe their new products will overcome. Here’s where the projects stand:

  • A vaccine developed by Pfizer and Valneva, which induces the development of antibodies in people to stop the disease-causing bacterium within ticks, entered a phase 3 human trial last month.
  • The medication developed by Klempner and colleagues at MassBiologics, which they call a vaccine alternative because it directly delivers a monoclonal antibody rather that spurring development of multiple antibodies in patients, is aiming for a phase 2-3 human trial next spring.
  • Researchers at the Yale School of Medicine report promising results from animal studies with a vaccine that teaches the body to recognize tick saliva and send an immune response to the site of the bite before the bacterium is transmitted.

If any of these products are eventually approved by the Food and Drug Administration (FDA), it would put humans nearly on par with dogs; they can get four Lyme vaccines made just for them. The lack of a human version has little to do with the science of making one. Klempner knows that well, as he worked on one of two Lyme vaccines that showed strong clinical trial results in the 1990s.

“It was not very difficult to develop,” Klempner recalls of the vaccine, Imulym, made by Pasteur Merieux Connaught but never brought to market. “In terms of difficulty from a biological and medical standpoint, it was relatively straightforward.”

The new efforts build on the basic strategy of those vaccines.

The science of stopping Lyme

Creatures that spread diseases through bites — such as mosquitos that transmit malaria and raccoons that transmit rabies — usually deliver the virus, bacteria, or parasite instantly. But when a black-legged tick latches onto someone, it takes at least 36 hours to pass along the Lyme-causing bacterium, Borrelia burgdorferi, says Gary Wormser, MD, chief of the Division of Infectious Diseases at New York Medical College. That lag, he notes, provides time for antibodies to get into the tick’s gut and prevent transmission of the bacterium before it sets off an infection in the human.

What’s more, the bacterium “has virtually no machinery to survive mutation,” Klempner says, so that researchers can identify and stick with antibodies that eradicate the bacterium rather than having to keep up with mutated versions. (Rapid viral mutation is a main reason that scientists have yet to develop a vaccine against HIV.)

LYMErix, manufactured by what was then SmithKline Beecham, induced patients to produce antibodies that a tick would absorb from its victim’s blood and that neutralized Borrelia burgdorferiStudies showed the vaccine to be about 75% effective in blocking the disease. The FDA approved it in 1998.

“It wasn’t a perfect vaccine, but it was good,” says Eugene Shapiro, MD, professor of epidemiology and investigative medicine at Yale School of Medicine in Connecticut.

As a marketable product, however, LYMErix faced compounding drawbacks. Sam Telford, ScD, professor of vector-borne infections and public health at Tufts University in Massachusetts, who helped run the vaccine’s clinical trials, notes that Lyme was far less prevalent then and was more restricted to a few geographic regions, thus limiting the market for a vaccine. (The Ixodes ticks that can carry Lyme disease, commonly known as deer ticks, have been most common in the northeast, Mid-Atlantic and north-central states, but their reach has been expanding.)

That, along with Lyme being seen as “easily treatable if you catch it at the early stages,” led the Centers for Disease Control and Prevention (CDC) to issue a “lukewarm recommendation” for the vaccine as rarely necessary and prompted many doctors to shrug it off, Telford recalls. Potential consumers felt lukewarm as well, for reasons that included the inconvenience of the three-dose regimen of injections over 12 months, uncertainty over how long the protection would last, and the absence of approval for use on anyone under 15 because LYMErix was not tested in children.

“The final blow,” Telford says, was claims by some recipients that the vaccine induced a form of arthritis. Although an FDA analysis of side effects among vaccinated people found no evidence to support the allegation, LYMErix sales fell under the weight of the negative publicity and a class action suit. The manufacturer (renamed GlaxoSmithKline) withdrew the vaccine in 2002.

That experience chilled research into prophylactic treatments against Lyme, Klempner says, even though “biologically, it’s an easy target.”

More disease spurs more research

Over the past 20 years, cases of Lyme disease have multiplied and spread , with experts citing climate change (which can make cold areas more hospitable to the tick’s lifecycle) and the increasing encroachment of human development adjacent to forested animal habitats.

“Lyme disease is all over the place in much of the U.S.,” Telford says.

Nailing down its prevalence is tricky. The CDC says it gets about 30,000 reported cases from doctors each year, but notes that this number does not reflect  all diagnosed cases. An analysis based on private insurance claims , conducted by CDC researchers, estimated that each year 476,000 people in the U.S. are diagnosed and treated for the disease. (Some people are treated based on symptoms without confirmation of having Lyme.) A recent report from the nonprofit FAIR Health, which studies health care costs and coverage, found that from 2007 to 2021 Lyme diagnoses rose 357% in rural regions and 65% in urban areas.

The growth of cases and public awareness have encouraged researchers that a market exists for prophylactics against Lyme. “The medical need for vaccination against Lyme disease is steadily increasing as the geographic footprint of the disease widens,” Pfizer and Valneva said in a news release last month about their vaccine project.

Here is a summary of the three most advanced development projects:

Pfizer and Valneva: Their vaccine, VLA15, induces the patient to create antibodies that block a protein, OspA, on the surface of the Borrelia burgdorferi bacterium. “Blocking OspA inhibits the bacterium’s ability to leave the tick and infect humans,” the companies state.

The vaccine requires three doses. With a phase 2 trial showing promising results in producing immune responses, the companies have started a phase 3 trial to enroll approximately 6,000 participants, ages 5 years and up, at 50 sites where Lyme is prominent. Because the vaccine produces antibodies to combat strains of the virus in Europe as well as the United States, there are test sites in the U.S., Finland, Germany, the Netherlands, Poland, and Sweden.

Shapiro notes that this vaccine does not include an epitope — the part of a molecule to which an antibody attaches itself — that was implicated in the arthritis claims against LYMErix.

The companies say they hope to have the vaccine licensed in 2025.

MassBiologics: Rather than prompt a patient to produce antibodies, the Lyme Pre Exposure Prophylaxis (Lyme PrEP) delivers a monoclonal antibody — a lab-made protein that binds to the surface of the bacteria — against the common U.S. strain of Lyme. Like VLA15, this medication targets the OspA protein.

Lyme PrEP conveys immunity almost immediately, Klempner says, as opposed to the weeks it might take a person to develop antibodies on their own after several shots. “The person is immune within hours or days,” he says.

In addition, Klempner notes, one antibody is less likely to trigger adverse effects in a patient than a medication that involves numerous antibodies, and the shot would be given once a year, at the start of tick season.

With a phase 1 trial showing no significant adverse effects, Klempner, former executive vice chancellor at MassBiologics, hopes a phase 2-3 clinical trial to test effectiveness can start in spring 2023. 

Yale SOM: Yale University researchers designed a vaccine that recognizes a tick’s saliva and sparks a skin reaction that makes it hard for ticks to hang on and feed. Created with mRNA technology — which helps to accelerate the production of vaccines, such as those against COVID-19 — this medicine quickly produces redness at the site of a tick bite, alerting victims to the bite and increasing the chances that they can remove the tick before it delivers the Lyme-causing bacterium.

“If you can remove the tick that was on for less than 36 hours, you’re not going to get Lyme,” Wormser says.

Trials on guinea pigs showed that when ticks were removed after redness appeared, none of the immunized animals developed Lyme disease. In addition, the “ticks fed poorly” and detached sooner than normal, Yale reports.

Moving forward

These advances provide hope for a Lyme disease vaccine within several years. Yet researchers offer caution. They warn that people vaccinated against Lyme will have to take precautions against other diseases that ticks transmit, like by wearing long-sleeved clothing in wooded areas and inspecting themselves for ticks after forest forays.

“It’s not like you can go out and say, ‘I’m vaccinated, I don’t have to worry about tick bites,’” Telford says. “There is no such thing as a good tick bite.”

Humans Have Paved the Way for a Global Lyme Disease Epidemic

Carved-up forests, biodiversity loss, and climate change may not have caused the tick-borne scourge, but they have enabled it

On the day after Christmas in 2015, I took a walk with my 30-year-old son in an old cornfield that long ago morphed, with changing patterns of agriculture, into a gently tended meadow we know well. This nine-acre patch of earth, across the dead-end lane from our home in upstate New York, has a rare and wonderful feature that we have worked, with the cooperation of neighbors, to sustain: a mowed trail around its perimeter that allows access even when summer mustard, milkweed, and goldenrod are four feet high and the blackberry brambles profuse.

photo of ticksPhoto by Jeb BjerkeTicks have changed daily life in communities across the US and much of the world, and the diseases they infect humans with have altered the course of many lives.

As we often do, we took with us that day a coterie of mismatched family dogs — a Shih tzu, Chihuahua, springer spaniel, and a beige rescue that we call a boxer.

The day was unusually balmy in the last week of a year that had gone down as the warmest in 135 years of weather history, followed only — but considerably — by the year before. The temperature had topped out at 55 degrees Fahrenheit that December 26th; it had reached into the mid-60s on Christmas and hit 72 in nearby Poughkeepsie the day before. For that time of year, daytime temperatures at or near freezing would have been far more typical here in the Hudson Valley, a hundred miles north of New York City. Instead, it had been so warm that forsythia buds had sprouted in one neighbor’s garden; crocuses peaked through in another’s.

When we came back from our short walk, we did what has become in New York State a routine practice from spring through fall, but not for winter. We checked the dogs for ticks. When we were done, we had picked twenty-one blacklegged ticks from the scruffs of our pups, each about the size of a small freckle, and all with one goal in mind: to latch onto a warm body and suck its blood.

When I moved to this rural county in upstate New York 30 years ago, such things did not happen. Ticks certainly did not show up in December, were indeed rare, and, if seen, were usually of the easier-to-spot dog tick variety, which infrequently carried Rocky Mountain spotted fever. They did not pack the potential arsenal of infection of the small, ubiquitous blacklegged ticks of today. Every year, the list of diseases found within this tick grows longer, including new bacterial, viral, and parasitic pathogens.

These infections have changed daily life in the county in which I live, and they have altered the course of many lives, particularly when they go unrecognized for weeks or months. Mention Lyme disease at a gathering here and nearly everyone has a story. The odd rash, fever, occasional palsy, meningitis, and joint pain of early stages. The sometimes-crippling arthritis, memory loss, depression, numbness, and fatigue of advanced disease.

Even the rare infection that can kill. In towns near me, Lyme carditis, in which the bacterium quickly cripples the heart, claimed a 17-year-old high school boy and a 38-year-old father of three within five months. A woman, who at 91 was an active gardener, died after being bitten by a tick and contracting another common tick-borne disease, babesiosis.

Blacklegged ticks have taken up residence in half of continental America’s counties, spreading west, north, and south from the Connecticut town for which Lyme disease was named in the late 1970s, like some unchecked algal bloom. These eight-legged arachnids have turned childhood from a time to explore nature to a time to fear it. My seven- year-old grandson has been warned since he could walk: Don’t brush up against the tall grasses at the edge of the trail. Don’t venture into the weeds. Tuck socks into pants. Sit still for repellent. Check yourself, and remind Mommy to also.

Then, pray we see the tick, and pity the parent who doesn’t know to look. Guidance counselors and teachers have told me of children, the most frequently infected, missing months, sometimes years, of school because the tick went unseen or the symptoms were misconstrued. But happenstance is not the only reason that cases are missed or treatment delayed, I have learned. Many patients have suffered needlessly, in the United States, Canada, England, France, Germany, and many other countries, because of how Lyme disease has been framed in American medical journals and treatment guidelines. This is an illness that has been minimized, underestimated, and politicized to the point that doctors fear treating it aggressively with a cheap, common drug: antibiotics.

I began to write about Lyme disease as an investigative reporter for a Dutchess County, New York, newspaper in 2012. I intended to write one or two stories about a prevalent local disease, focusing on its origins, growth, and management by health officials. But Lyme disease proved to be a story far beyond the parameters I’d envisioned. Over a period of four years, I studied the policies, paper trail, and scientific literature. I tested the postulates of patients and their advocates. Many of their assertions, I concluded, were true.

Decades-old testing protocols failed to diagnose many people with the disease. The risk of overtesting — and falsely diagnosing people with Lyme disease — was exaggerated at the expense of cases missed and symptoms dismissed. Official figures did not reflect the epidemic’s scope and were soon revised tenfold. Human trials concluded that short-term antibiotics eradicated the bug, while animal and test-tube studies showed they didn’t.

And then there was the politics of Lyme disease. Doctors who prescribed repeated courses of antibiotics — standard in other diseases — faced professional disciplinary charges, huge legal fees, and sometimes suspension or loss of their licenses. Research was discredited, ignored, or relegated to second-tier journals when it challenged prevailing dogma. Scientists who were invested in a benign view of Lyme disease used access to elite journals to uphold the status quo. And little money was available for treatment trials because the medical system purported to have the answers to Lyme disease care.

And yet, some 10 to 20 percent of people infected annually with Lyme disease, estimated at 380,000 Americans in 2015, have symptoms that linger months and sometimes years after treatment. The United States Centers for Disease Control and Prevention (CDC) calls the condition Post-Treatment Lyme Disease Syndrome, and it affects multitudes of people as disease-toting ticks move around the world. Lyme disease is rife in most every country in Western Europe. It is in Russia, China, former Soviet satellite states, and though officially unrecognized, in Australia too. In one small study, half the ticks in two parks in New York City harbored the Lyme disease pathogen. In a Chicago park, Ixodes ticks, some laden with the Lyme pathogen, outnumbered every other tick carried by migrating birds in 2010; five years earlier, there were none. In a northwestern suburb of Beijing, one in twenty residents tested positive in a Chinese study that said, quite remarkably, “Underdiagnosis of early Lyme disease and physical damage at advanced stage are huge problem [sic] in this area.”

But infected ticks haven’t just moved around. They have added layers of woe. Forty-five percent of ticks in the French Ardennes, for example, carry more than one disease; some have five. A tick-borne malaria-like illness, babesiosis, unheard of not so long ago, became a nationally reportable disease in 2011 after cases skyrocketed in some American states — and it slipped into the US blood supply, infecting premature babies and killing at least eight people. Another rapidly emerging pathogen, Borrelia miyamotoi, prevalent in the San Francisco Bay area, has upped the ante on Lyme. Tick babies, hatching by the thousands, can inherit the bug directly from mom rather than get it with its first animal blood meal. Add to this Powassan virus, which is also passed to baby ticks, transmitted within fifteen minutes of a bite, and is fatal 10 percent of the time, and anaplasmosis, a bacterial infection that is particularly dangerous for the elderly. Now consider how a tick infected with two or three of these organisms, for which a doctor may not know to look, and for which testing is not routine, can wreak havoc in a human body.

This spreading toll of tick-borne disease is not a random act of nature. By virtue of the developed world’s lifestyle and influence — the cars, the suburban tracts and carved-up forests, the diminished biodiversity, the emissions and airplanes — we have paved the way for the first global epidemic abetted by climate change. Warming may not have caused this scourge, but it most certainly is enabling it.

The pathogen that causes Lyme disease, Borrelia burgdorferi, has existed in the environment for millennia, just as blacklegged ticks have long been transported on the wings of birds to new and far-flung climes. What is different is that they now survive there. We have revived and empowered a sleeping giant, the Borrelia bug, by helping to create conditions favorable to the ticks that deliver it.

Climate change alone hasn’t done this — ticks thrive amid the mice and deer so prevalent in an attenuated, postindustrial era — but its influence in supporting ticks, the vector of human transmission, is key. Ticks have climbed latitudes like ladders; they have moved up mountains. Driven by warmer winters and earlier springs, they are predicted to move well north into Canada in coming years, just as they migrated up the Atlantic seaboard and north into Scandinavia at the close of the twentieth century.

Lyme disease, of course, is not the only epidemic to blossom in our changing world. Illnesses carried by mosquitoes — Zika, West Nile, Chikungunya, dengue fever, malaria — are proliferating and are predicted to worsen as the globe warms. The diseases they carry today annually cause millions of illnesses in tropical countries — and in the case of malaria, nearly a half-million deaths.

When these illnesses arrive on US shores, they capture the public imagination and lead the nightly news in a way that Lyme disease never has. Yet the Lyme toll in the United States and many developed countries is far higher — perhaps four or five million Americans infected to date — than West Nile, Zika, and all other mosquito-borne illnesses combined. And like West Nile, Lyme sometimes kills, although the numbers are largely unknown. Late-stage Lyme disease has even led to suicide, an outgrowth both of the illness and society’s regard for it.

For official purposes, Lyme disease is not called an epidemic. It is an “endemic,” a term with far less urgency, reserved for an illness that comes to stay. It emerges. It takes root. And it does not leave. It is a slow burn, this scourge, established, entrenched, and for many, inescapable. But its second-class status also stems from how Lyme disease has been managed and shaped. Treatment guidelines issued by the Infectious Diseases Society of America (IDSA) in 2006 diminish the lingering symptoms of Lyme disease sufferers, calling them the “aches and pains of daily living.” This, while studies from Columbia University, Johns Hopkins, and elsewhere have measured significant neurological, cognitive, and physical impairments in treated patients. One study equated the quality of life of those with longstanding Lyme disease to people with congestive heart failure. Others have linked the disease to mental illness and showed brains deprived of blood flow.

Borrelia burgdorferi is a clever, adaptable bug. It has a hugely complex genetic profile, with more independently replicating structures, called plasmids, than any other bacterium. It doesn’t need iron, unlike most other bacteria, removing one option for our immune systems to starve it into submission. It grows slowly, confounding drugs that work on rapidly dividing cells. It hides in places that diagnostic tests do not reach. This tiny spiral-shaped organism is actually a boon to ticks. Those infected are more likely to find a blood meal, and ominously, may even cope better in dryer, hotter conditions, than those that do not carry the Lyme pathogen.

In 2014, a report by the Intergovernmental Panel on Climate Change, a multinational effort, said the period from 1983 to 2012 was likely the warmest 30 years in the Northern Hemisphere of the previous 1,400 years. The report, relying on multiple, independent temperature and climate indicators around the globe, called this “robust multi-decadal warming.” Tellingly, the US government monitors Lyme disease as a key indicator of the effect and pace of climate change. Like millions of other people, I see this change in my everyday life. It means that on a short walk in late December, I found twenty-one ticks on four panting, happy dogs that like nothing better than a romp through our shared preserve.

When I look at that lovely field, I see something else. I see a beautiful, inviting menace, a dark and dangerous wood. I see the first epidemic in the era of climate change, long in the making, global, and here to stay. Call it, if you will, the first pandemic. There are things we can do to protect ourselves, to control the bug, to limit its spread. You will read about that in this book. But you will read also about the missed opportunities, the misconceptions, and the human contribution to an epidemic that, for now at least, is beyond our ability to stop.

How to Protect Yourself from Ticks and the Dangerous Diseases They Spread

Summer is the season for stone fruit, pool parties, cookouts and, increasingly for Americans, ticks.

Ecologist Felicia Keesing had an uncanny sense for ticks for as long as she could remember. If one bit her, she could feel it and would quickly pluck it off with tweezers. But last year this superpower failed her when she didn’t feel a tick latch on. Keesing tested positive for Lyme disease, a tick-borne illness caused primarily by the bacterium Borrelia burgdorferi, after finding the telltale bull’s-eye rash on the back of her knee. She started an antibiotic regimen right away and had no further symptoms, but the experience troubled her.

“It felt like I was being hypervigilant when I was doing checks [for bites] and things,” says Keesing, who studies the parasitic arachnids at Bard College in Annandale-on-Hudson, N.Y., where ticks are thriving. “So I’m a little warier this year.”

Keesing’s wariness is justified. Tick-borne diseases have been booming in the U.S., and tick abundance could spike this summer. Populations of rodents, a key host for ticks, are predicted to increase this year thanks to a large acorn crop in 2021.

Roughly the size of a sesame seed, these semimobile sacks of blood trail closely behind mosquitoes for the top transmitters of disease. Ticks are responsible for about 75 percent of the 650,000 vector-borne disease cases that occur annually in the U.S. New England and the Upper Midwest have seen the lion’s share of increase in tick-borne illnesses, such as Lyme disease, anaplasmosis and babesiosis. Last month Maine recorded its first-ever death from the rare, tick-associated Powassan virus. But over the past few decades, various species of ticks have been migrating to new regions, leading to an increase in Rocky Mountain spotted fever cases throughout the South and mid-Atlantic.

“No matter where you are in the contiguous U.S., you can run into a different tick,” says Rebecca Eisen, a research biologist at the Centers for Disease Control and Prevention.

Two side-by-side maps of the U.S. from 2001 and 2019 show that Lyme disease cases have spread geographically throughout the Northeast and the Midwest.
Credit: June Kim; Source: Lyme Disease Map, Centers for Disease Control and Prevention (data)

The CDC does not actively track tick populations, so researchers typically rely on disease rates to study the parasite’s spread. The geographical spread of ticks has put more people at risk, but Keesing says it’s unclear whether risk has increased for communities with already high tick counts. While it’s tricky to predict the areas that will have more dangerous tick conditions, one thing is true: “If you live in an area with tick-borne diseases, and most people in the United States do, you should educate yourself about the times of year and the kinds of habitats that put you at risk,” Keesing says.


Ticks have four life stages: egg, larva, nymph and adult. At each stage after they hatch, they need to feed on the blood of hosts to molt and enter the next phase. Different tick species feed on certain animal species to survive. When a tick feeds, it may also pick up pathogens residing in the host’s blood—pathogens that may have been left behind from other ticks.

“If you’re a pathogen, being in the blood is not only a good way to get around someone’s body; it’s a good way to get picked up by [any] blood-feeding arthropod and get transported to a new host,” Keesing says.

Pathogens don’t automatically transfer once a tick latches on. Many ticks lack disease-causing viruses and bacteria in the first place, and even if they are present, different pathogens transmit at different rates. Some pathogens, such as the Powassan virus, can transmit in just 15 minutes. Borrelia burgdorferi, the pathogen that causes most Lyme disease cases, takes at least 36 hours to travel from a tick’s gut into a host’s bloodstream. Diagnosing Lyme disease is tricky because B. burgdorferi stays in the skin initially after being transmitted, leaving comparatively low levels of antibodies in the blood for a few weeks that make the disease difficult to detect.

Eisen says bites shouldn’t be taken lightly. Tick-borne diseases can cause severe symptoms, such as joint pain, nausea, facial paralysis—and even an allergy to red meat. Fatal cases are very rare, but it’s important to be aware of ticks and the dangerous pathogens they carry.

There are 30,000 cases of Lyme disease reported to the CDC every year, but most experts agree that figure is a substantial undercount. One study suggests that there are potentially half a million annual Lyme disease cases in the U.S. Lyme disease receives the most attention and has the highest case count among tick-borne diseases, but there are 17 other known pathogens that cause human illnesses, and six new illnesses have been discovered in the past 20 years. Scientists believe that a greater awareness of illnesses, rather than an expansion of the pathogens picked up by ticks, is responsible for the increase in illness types.


Ticks and tick-borne illnesses are on the uptick because of three factors: climate change, an increase in tick habitats and a growing awareness among health professionals.ADVERTISEMENT

Warmer temperatures and increased humidity caused by climate change are likely making it easier for ticks to survive in northern climates and thus increasing the potential for disease transmission, though some studies suggest that a dry summer could kill and regulate the spread of the parasites. Many of these studies were conducted in a controlled laboratory setting, however. A recent study tracking ticks’ survival rates outdoors showed a surprising resilience to extreme hot and cold temperatures.

“Ticks are little tanks,” says Keesing. “We look at them as being fragile, but they move up and down in the forest soil to [regulate] their temperature.”

While scientists are unsure how weather patterns affect or predict summer tick activity, they do know that as ticks’ geographical range increases, tick-borne illness also increases. Tick populations are typically lower on the West Coast than in the eastern U.S., but Lyme disease rates have been rising in California as well.

Tick-borne diseases spread through the migration and behavior of animal hosts. For example, deer and rodent habitats are increasingly overlapping with human communities—and all three species are hosts for the blacklegged tick, also aptly named the deer tick. As humans have built more homes on the edge of forests, deer and rodents have brought this tick species into homes, yards and other infrastructure.

Without a host, ticks don’t move great distances—barely three feet in 30 minutes, according to one study. “They’re not going to chase you when you’re out running, they’re not going to fall from the trees, and they don’t fly,” Eisen says. “But it’s good to be aware that there is a risk and take precautions” if you go outdoors.

People should stay vigilant, especially because many tick-borne diseases lack the bull’s-eye rash at the bite site, says Bobbi Pritt, who studies these diseases at the Mayo Clinic in Rochester, Minn. “Just like you should be putting on sunscreen,” Pritt says, “you should also be wearing a tick repellent and checking yourself for ticks when you come [home]. Just make it part of your routine.”


In order to avoid tick bites, wear long clothing, stuff your pant legs into your socks and consider treating your clothes with permethrin insecticide to avoid unwanted passengers. Environmental Protection Agency–registered tick repellents, especially those containing DEET, are also effective at keeping the parasites and other bugs away. Avoid obvious tick habitats such as shady brush, even if it’s in your own yard. When you return home, throw your clothes in the dryer and do a thorough check for ticks on your body. Ticks love nooks and crannies, so pay extra attention to damp spots such as your armpits or the backs of your knees. Also check your dogs because dog ticks can carry Rocky Mountain spotted fever, which can also infect humans.

Even with these preventive measures, if you see a tick lodged on you, skip the matches or nail polish and resist the urge to pick it off with your fingers—you’ll only leave the tick’s mouth lodged into the skin. Instead use tweezers and pluck at the site of the bite as close to the skin as possible. If you’re planning to go camping in areas with known high tick counts, carry fine-tip tweezers—they could save your life. The CDC advises to consult your health care provider after noticing a tick bite if you start to experience flulike symptoms such as headache, chills or fever. It’s always best to catch tick-borne illnesses early.

Tick-borne diseases are scary, and the geographical spread of ticks into new communities is concerning, but don’t let the fear of a tick bite keep you from enjoying a beautiful summer day outdoors. Just keep a careful eye out for those pesky parasites, Keesing says.

“None of [these preventative measures] makes being outside feel all that glamorous,” she says. “It takes away some of that sense of freedom that we feel, but I’ve been living in this area for decades now, and it just becomes part of your practice. It’s just what you do.”

2023 may be the worst tick season ever. Here’s how to protect yourself.

As people enjoy the outdoors this summer, they should remember they’re not the only ones taking advantage of the warm weather. Warmer springs and longer summers means a longer tick seasonSeveral states’ health officials are already warning of a particularly bad year for ticks, and the Centers for Disease Control and Prevention reported earlier this year that cases of the tick-borne disease babesiosis have been rising.

”This is this is the time of year where, in lots of parts of the United States, a lot of people are getting exposed to ticks,” Lyric Bartholomay, an entomologist at the University of Wisconsin-Madison, says. They might be worse this year because it warmed up sooner than it has in previous years. “Tick activity will ramp up as the temperatures rise, and if we have an early spring, then it’s going to seem bad because suddenly we’re seeing ticks at a time of year where we haven’t seen them before.”

The best way to avoid a tick-borne disease is, obviously, not to get bitten by a tick. “When you’re out in the wild and you see those signs that say ’Don’t feed the animals,’ they mean don’t feed the bear and rodents, but I think that should apply to the invertebrates too,” Bartholomay says. “We should just really try not to feed the bloodsuckers either.”

Close up of a hiker's boots, where they have tucked their pants legs into their socks.
Tucking your pants into your socks is an effective way of preventing ticks from reaching the skin on your legs.PHOTOGRAPH BY ALEX TREADWAY, NAT GEO IMAGE COLLECTION

Here’s what to know to protect yourself from ticks and what to do if you’re bit.

How can you protect yourself from ticks?

The two keys are wearing the right clothes and using repellent when in areas with ticks.

“If you’re walking through grassy or forested areas, wear long pants and long sleeve shirts, and then you check your clothes and skin for ticks when you come back,” Timothy Brewer, an infectious disease physician and epidemiologist at the University of California Los Angeles says.

Bartholomay also recommends wearing light-colored clothing so it’s easier to see ticks, and tucking your pants into your socks so they can’t crawl up your pant leg.

”I think there’s a little bit of a fear that ticks are going to drop out of the trees, and that’s not really how ticks work most of the time,” says Michael Reiskind, an entomologist at North Carolina State University. Since they’re usually looking for smaller animals, they’re often latching on somewhere from the waist down and then crawling up.

Use a repellent that says it repels ticks, which includes those containing DEET. The percentage of DEET determines how long it lasts, so if you’ll only be in ticks’ home for an hour or so, a lower percentage is fine, Reiskind says. If you’ll be out longer, up to 25 percent is wise, or re-apply the repellent. The insecticide permethrin on your clothes can also repel ticks.

When checking yourself for ticks, look around your ankles or legs if you’ve been out a short time, Reiskind said. But if you’ve been out for several hours or few days, they could have migrated anywhere, so have a friend or family member check your back and hairline as well.

Female Marine recruits are seen standing in the clearing of a wooded area as they spray themselves and each other with bug spray.
To guard against mosquitoes and ticks, Marine recruits spray each other with insect repellent during boot camp training at Parris Island, South Carolina.PHOTOGRAPH BY LYNSEY ADDARIO, NAT GEO IMAGE COLLECTION

What do you do if you find a tick on yourself?

You should remove the tick, but be sure to remove the whole organism, including the mouthparts. Use tweezers to get a firm grip where it’s attached and firmly but steadily pull upward without jerking. Never crush a tick, and don’t grab the tick by the midsection or you risk squeezing its contents back into your body, Bartholomay said. She also said never to use Vaseline or a match or any item mentioned in other old wives’ tales to remove a tick.

The CDC offers step-by-step instructions, including a Tick Bite Bot that walks you through removing a tick and seeking care. Afterward, clean the bite area and your hands with rubbing alcohol or soap and water, the CDC recommends.

How do you know you’ve been bitten by a tick?

There’s unfortunately no way to easily tell a tick bite from another critter’s bite, such as a spider or mosquito bite, Reiskind says. “The only way you really know if you’ve been bitten by a tick is if you find the tick embedded in you, in the act of biting you,” he says.

But ticks don’t just bite and run. They settle in to get their fill of blood, and adults stay on for a day or two before becoming fully engorged, so many people find the tick before it drops off. Nymphs are much smaller—the size of a poppyseed—so they’re harder to see and may drop off before you ever see them.

A tick bite is usually a red raised bump like a nasty mosquito bite. If a rash is present, you’ve developed an infection, though it’s not possible to tell what kind by the rash alone. The distinctive bull’s eye rash many people associate with Lyme disease can be caused by other tick-borne pathogens, Reiskind says, and it’s still possible you’ve contracted a disease if the rash looks different or if there’s no rash at all.

What should you do if you’ve been bitten by a tick, or suspect a tick-borne disease?

Symptoms of a tick-borne disease include fever, headaches, joint aches and pains, and a rash, Timothy Flanigan, an infectious disease physician at Brown University, says. If you develop a fever, malaise, or a rash after being in an area where ticks are active, Flanigan and Brewer recommend getting evaluated at your primary care doctor or an urgent care clinic.

“As long as you’re not critically ill, you probably don’t have to go to a hospital emergency room,” Brewer said. Although you can be tested for tick-borne diseases, the tests detect antibodies, which can take a few weeks to show up in your blood, he says. “If we have a reasonable suspicion for tick-borne infection, we would just go ahead and treat it. We wouldn’t wait for the test to come back.”

If you find an engorged tick on your body that’s clearly been there a while, you’re at higher risk for a disease. If it’s a blacklegged tick, you can see a doctor for doxycycline, an antibiotic which can help prevent Lyme disease from developing or treat it after it develops, Brewer and Flanigan say. Many other tick-borne diseases caused by bacteria are treated with doxycycline as well, but parasitic diseases, such as babesiosis, may require a different remedy, and viral disease, such as the Heartland virus or Colorado tick fever, don’t have any treatments other than supportive care.

If you keep the tick after removing it, Flanigan noted that several companies will test it for pathogens. Though, the CDC doesn’t recommend these testing services since evidence of a pathogen doesn’t guarantee you were infected. But some people want to know what their risk is, and if symptoms do develop, you can tell your doctor what the results are.

Where in the U.S. are hotspots for ticks and tick-borne diseases? 

Ticks are found everywhere across the U.S., though “different geographic parts of the country have a different geographic pattern of disease,” Flanigan says. He recommends the CDC’s website on ticks to identify types of ticks, diseases they carry, and where they’re found.

The blacklegged tick, which transmits Lyme disease, has historically been a problem mostly in the northeastern U.S., but it’s been spreading south and west and now lives throughout the whole eastern half of the country, with increasing cases in the upper Midwest and the mid-Atlantic states.

But plenty of other types of ticks carry different diseasesEhrlichiosis is found throughout the southeastern and south-central U.S. as far west as Texas, and the Rocky Mountain wood tick— which can transmit Rocky Mountain spotted feverColorado tick fever, and tularemia—is found throughout the West and Pacific Northwest. Babesiosis occurs most frequently in the Northeast and upper Midwest, but cases have occurred throughout other U.S. regions, including the West Coast.

So, no matter where you are this summer, be vigilant: check your body for ticks, use a repellant, and wear appropriate clothing. And, if you are bitten, don’t panic.

This tick bite could make you allergic to red meat—and it’s spreading

Alpha-gal syndrome, spread by bites from the Lone Star tick, was originally found primarily in the southeastern U.S.—but is now moving north and west as temperatures warm.

Alpha-gal may sound empowering, but the nickname, short for galactose-alpha-1, 3-galactose, is a sugar molecule that might just cause you to become allergic to meat.The sugar molecule is spread from the Lone Star tick bite, named for the single star-shaped spot marking on its back. 

A new study by the Centers for Disease Control and Prevention found that the number of suspected cases in the United States has increased substantially since 2010—and some were identified in states not typically known as stomping grounds for these bloodsucking parasites.

Once bitten by a Lone Star tick, the body’s immune system is rewired.

“You’re walking through the woods, and that tick has had a meal of cow blood or mammal blood,” explains Cosby Stone, an allergy and immunology fellow at Vanderbilt University. “The tick, carrying alpha-gal, bites you and activates your allergy immune system.

“From this, your body creates alpha-gal antibodies and, from that point on, the body is wired to fight alpha-gal sugar molecules. The majority of people who develop alpha-gal syndrome (AGS) realize their illness after eating meat, which is rife with alpha-gal. The sugar is also present in some medications that use gelatins as stabilizers.

“There’s a time delay in the reaction,” says Stone, which accounts for why some people don’t always immediately realize they’re having a reaction. “It [the alpha-gal] has to first travel through your gastrointestinal tract to be released. Hours later, patients wake up with hives, shortness of breath, vomiting, and diarrhea.”

In rare cases, patients have to be admitted to the ICU.

“Some patients have had to be given life support because their blood pressure is so low that they’re in eminent danger of dying,” says Stone, who has treated those suffering a reaction.

“Most patients don’t know what they have,” he explained. It often takes repeated allergic reactions for people to link their diet to their outbreak. Repeated exposure to tick bites can also worsen the severity of a reaction. Those who developed more alpha-gal antibodies from more exposure to ticks saw the most serious symptoms.

The allergy so far has treatments for side effects but no cure or vaccine.

Is it on the rise?

Originally found primarily in the southeastern U.S., the disease may become more common in farther north and western regions that experience warming temperatures.

The CDC  does not log cases of AGS, so most of the previous reports of the rise in suspected cases have been anecdotal. But the new study—which examined antibody testing results submitted to the laboratory responsible for nearly all testing in the U.S.—found that the number of people who tested positive for AGS spiked over a five-year period: from 13,371 in 2017 to 18,885 in 2021.

Until cases were first identified about a decade ago, little to nothing was known about the origin of this meat allergy.

“The awareness of alpha-gal has grown,” notes Stone. “It’s also possible that because allergies in general are going up, reactions to alpha-gal are increasing.”

Studies have documented that warming temperatures have led to an increase in plant-based allergies from allergens like pollen.

Stone believes advancements in hygiene have led to a weakening of some of the natural immunity we develop to fight allergies.

In an interview with USA Today, Purvi Parikh from the Allergy and Asthma Network warned that as the climate has warmed, ticks have begun to spread their territory farther north.

Regardless, humans come into contact with ticks more frequently during warmer weather, and Stone recommends warding off alpha-gal in the same way other tick-borne illnesses are prevented: use insect repellent, pretreat clothes, and avoid high grass and shrubbery.


nationalgeographic.com, “Lyme disease is spreading fast—but a vaccine may be on the way.” By Sharon Guynup; ucsf.edu, “Lyme Disease is On the Rise – An Expert Explains Why.” By Nina Bai; mayoclinic.org, “Lyme Disease.”; health.ny.gov, “Lyme Disease (Tick-borne borreliosis, Lyme arthritis) Fact Sheet.”; theguardian.com, “What’s really behind the spread of Lyme disease? Clue: it’s not the Pentagon.” By Peter Beaumont; aamc.org, “Lyme disease is on the rise. Why is there still no vaccine? Two decades after a vaccine was withdrawn, scientists are producing new medicines to fend off a disease that experts estimate afflicts nearly half a million people each year.” By Patrick Boyle; earthisland.org, “Humans Have Paved the Way for a Global Lyme Disease Epidemic: Carved-up forests, biodiversity loss, and climate change may not have caused the tick-borne scourge, but they have enabled it.” By Mary Beth Pfeiffer; scientificamerica.com, “How to Protect Yourself from Ticks and the Dangerous Diseases They Spread.” By Timmy Broderick; nationalgeographic.com, “2023 may be the worst tick season ever. Here’s how to protect yourself.” By Tara Haelle; nationalgeographic.com, “This tick bite could make you allergic to red meat—and it’s spreading.” By Sarah Gibbens;

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